A power plant typically converts an energy source such as moving water (dam), nuclear, natural gas, or coal to electricity. One type of energy conversion process uses heat to generate electricity. For example, natural gas is ignited with air to create a hot gas. The hot gas is directed through a compressor to a power turbine. The power turbine has blades that are induced to spin by the hot gas. The rotational motion of the power turbine is coupled to an electrical generator. The system is made more efficient by recovering the hot gas that has passed through power turbine in a heat recovery steam generator that is then coupled to a steam turbine that further drives the electrical generator.
Many components of a natural gas power plant such as a transition duct and heat exchangers are exposed to extremely hot gases at temperatures approaching 3000 degrees Fahrenheit. The composite materials used to make these components are specifically designed to handle the adverse conditions in which they operate. Furthermore, the composite materials are formed into complex shapes. The high heat and oxidizing environment that these components are subject to introduce long term reliability problems that increase the cost and maintenance of a system. In general, the components cannot be cast, forged, or formed from a single sheet of material because of structures that are formed within the component. For example, cooling channels within the walls of material are often necessary to reduce the heat on the component. This problem is not isolated to the energy industry, for example, the air craft and rocket industries have almost identical problems.
One method of fabrication to produce a composite material is to form it from more than one sheet of material. The components which make up the composite material are bonded together. Typically, the composite material will have at least one feature or void internal to the structure. As mentioned above, cooling channels or passages are often desirable in a component having a surface exposed to high temperatures. A manufacturable method to construct a formable composite material having an internal feature such as a cooling channel is created using three sheets of material. A center sheet is machined or stamped having grooves or cut outs corresponding to the internal channels. A sheet of material is placed on either side of the center sheet. The three sheets are then bonded together. The composite material can then be cut and formed into the appropriate shape. Typically a brazing process is used in conjunction with extensive tooling to maintain interfacial pressure to bond the materials together to form a composite sheet. Residual braze alloys can introduce foreign elements that interfere with subsequent forming and or welding processes. Moreover, the quality of the bond of each sheet to the other may not be uniform and results in long term reliability issues requiring scheduled replacement. The cost to manufacture can skyrocket because the tooling can be unique to make each component.
Accordingly, it is desirable to produce a composite material that is stronger and more reliable. In addition, it is desirable to reduce the need for unique tooling and lower the cost of manufacture. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.